Shoulder replacement is a well-known and widely used technique which has been very successful. This is particularly important where the patient has disabling pain which is unresponsive to normal treatments and where the humeral head has suffered from osteoarthritis, rheumatoid arthritis and so on. In addition, a shoulder replacement may also he required following acute trauma situations where the humeral head has been fractured. In such circumstances frequently the bone in that area has been fractured into several pieces including separation of the humeral head or separation of the head and the greater and lesser tuberosities from the main part of the humerus.
The proximal humerus in many prior systems comprises a head and a stem and a number of radially directed ribs are provided at the proximal end. These have a strengthening function, and once the stem has been implanted into the proximal end of the humerus, they help to ensure that the stem cannot rotate relative the humerus. Such ribs include a lateral rib, a strengthening and supporting rib for the humeral head which is diametrically opposite this lateral rib, and, at right angles to these two ribs, a further pair of ribs that have a strengthening effect. The lateral rib is usually provided with a number of small holes, which can be used to suture a separated greater and/or lesser tuberosity into place to allow union with the main part of the bone if they have been fractured or osteotomised.
We have found in practice, however, that there are occasions when it is quite difficult to suture the greater and lesser tuberosities in place. This is particularly true when trying to tie a lesser tuberosity in place since this is somewhat displaced from the lateral rib, which itself tends to be embedded in the region where the greater tuberosity is or should be positioned.
Examples of successful shoulder prostheses include prostheses available under the trade designation "Neer II system" and "3M Modular Shoulder" from 3M Health Care Ltd., a subsidiary of Minnesota Mining and Manufacturing Company, St. Paul, Minn. Competing shoulder prostheses are also available. In addition, shoulder prostheses are disclosed, for example, in U.S. Pat. Nos. 3,916,451; 3,978,528; 4,179,758; 4,919,670; 4,919,669 and 5,462,563; PCT Patent Publication No. WO 96/17553; European Patent Publication Nos. EP 0 041 591; EP 0 127 503; EP 0 216 489; EP 0 299 889 and EP 0 639 359; British Patent Nos. GB 1,438,950 and GB 2,223,172; and German Patentschrift No. DE 195 09 037.